Electromagnetic device



June 26, 1923.:

W. H. D. FORD ELECTROMAGNETIC DEVICE Filed Nov. 6, 1920 /nveni0/': M'll/am /7.0. Fora.

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Patented June 26, 1923.

UNITED STATES PATENT OFFICE.

WILLIALML H. FORD, OF CHICAGO, ILLINOIS, ASSIGNOR TO WESTERN ELECTRIC COM- PANY, INCORPORATED, OF NEW YORK,

N. Y., A CORPORATION OF YORK.

ELECTROMAGNETIC DEVICE.

Application filed November 6, 1920. Serial No. 422,240.

To all whom it may concern:

Be it known that I, WILLIAM H. D. F0111), a citizen of the United States, residing at, Chicago, in the county of Cook, State of Illinois, have invented certain new and useful Improvements in Electromagnetic Devices, of which the following is a full, clear, concise, and exact description.

This invention relates 1n general to electromagnetic devices and more specifically to such a device in which the time of release of the movable member is comparatively lon I 11 various electrical systems it is necessary to insure that the operation of the various elements ofthe system follows a redetermined sequence, such is the case, or example, in many signaling circuits in which it is necessary,-for the proper functioning of the circuit, to insure that one'relay has sufiicient time for the closure of its contacts before a second relay operates to open its contacts. Accordingly, various types of relays have been developed which are known as quick acting, slow acting, or slow releasing relays and it is with the latter type that ,this invention is concerned. Heretofore the slow release feature has been obtained chiefly b the use of a short-circuited secondary win ing or by the use of copper sleeves about the core which serve as the equivalent of a very efiicient short-circuited winding. llhe function of such a winding or sleeve is to prolong the flux during the decay or falling off of the induced current of the secondary winding.

The object of the present invention is to produce an electromagnetic device in which the time of'release is considerably increased and moreover one in which this advanta e is obtained without departing appreciab y from the standard design of apparatus, or.

causing any considerable increase in its cost of manufacture. To attain this object and in accordance with a feature of the invention, there is provided a device in which the reluctance of the magnetic circuit is made very low when the device is operated so that the armature is maintained in the operated position until the flux generated by the decay of current in the short-circuited secondary winding is decreased to a smallvalue.

' his and other features of the invention will be more clearly understood by reference to the accompanying drawing in which Fig. 1 is a view in perspective of an electromagnetic device embodying this invention. Fig 2 1s a view showing the core of such a device together with the windings thereon, and Fig. 3 is a sectional view taken along the line 3-3 of Fig. 1' and in the direction indicated by the small arrows.

Referring now to the drawing, there is disclosed a flat type relay of the same general design as described in detail in Patent No. 1,156,671 of October 12, 1915 to E. B. Craft. This relay comprises a core 5 having a clamping portion 6, a substantially U- shaped armature 7 and contact springs 8-8 adapted to be operated by movement of the armature. The legs of the armature 7 are secured to the core' clamping portion 6 by means of flexible magnetic hm e members 9 to which are riveted pins 10 which fit loosely into perforations in the armature legs 7 and serve as trunnions. A member 11 of magnetic material is provided, as shown, to bridge the gap existing between the ends of the armature 7 and the core clamping portion 6, Upon the core 6is laced a winding 12 which is short circuited upon itself and an operating winding 13, the ends of which are soldered to terminal members 1414.

The core clamping portion 6, bridge member 11, hinges 9, terminals 14--14, and contact springs 88 are securely clamped together by means of screws 15--15 which thread into perforations in a clamping plate 16. Suitable insulating members 17-17 of hard rubber or similar material are provided to insure the necessary electrical separation of the parts. A threaded stud 18 of brass or other non-magnetic material is securely riveted to the core 6 and is provided with a split adjusting nut 19 which permits the ad- 'ustment of the air gap normally existing etween the end of the core and the armature pole face. To prevent the armature from coming into direct contact with the core, a stop pin is rovided, consisting of an internally thread ed split bushing 20 of brass, or similar material which is securely riveted to the end of the core, and an adjustable brass screw 21 which threads into this bushing.

Upon the flow of current through the operating winding 13, the armature is caused to move towards the core, and in its movement to operate the contact springs 8-8. As a. result of the loose pin construction, by

means of which the armature is secured to the core, the legs of the armature 7 are permitted to move slightly so that they come into intimate contact with the bridging member 11, thus reducing the reluctance of the magnetic circuit at the point where the armature is hinged to the core member. Upon the opening of the circuit through the winding 13, a current is induced in the closed secondary winding 12 and the armature remains in its attracted position until the flux through the magnetic circuit has died down to such a point as to be overcome by the pressure exerted by the contact springs 88. In view of the decreased reluctance of the magnetic circuit as a result of the construction described above, the armature is maintained in its operated position for a considerably longer period, thus increasing the time of release of the armature.

While the device embodying the structure described is particularly eflicientwhen employed in combination with a short circuited Winding, or its equivalent, the structure also is of advantage when used without such a Winding, since the low reluctance somewhat increases the time of release res-ultingfrom residual magnetism.

What is claimed is:

1. In an electromagnetic device, a magnetic circuit including an armature and a core, flexible means for securing the armature to the core, means co-operating with said armature and said core for decreasing the reluctance of the magnetic circuit at the point Where the armature is secured to the core. I

2. In an electro-magnetic device, a magnetic circuit including an armature and a core, an operating winding, means for prolonging the decay of the flux in said core after opening of the circuit through the operating winding, and means for decreasing the reluctance of the magnetic circuit when the armature is in its operated position.

3. In an electro-magnetic device, amagnetic circuit including an armature and a core, an operating winding, hinge members adapted to secure the core to the armature, and a magnetic member lying adjacent to the armature at the point Where the armature is secured to the core.

l. In an electro-magnetic device, a magnetic circuit, including an armature having perforations therein and a core, flexible means for securing the armature to the core, said means including a pair of hinge members having right angled extensions loosely fitting into the perforations in said armature, and a magnetic member bridging the gap between the core and the armature.

5. In an electro-magnetic device, a core, a U shape armature in alignment therewith, and flexibly secured thereto by means of a pair of hinge members having right angled portions fitting loosely into suitable perforations in said armature, an operating winding, a magnetic bridging member lying adjacent to each hinge portion, and to which the armature is drawn into intimate contact upon the flow of current through the operating Winding. and means for prolonging the flow of flux through the core.

In witness whereof. I hereunto subscribe my name this day of @ctober 29th A. I), 1920.

WILLIAM H. D. I QRD. 

